Research On Flotation Machine And Its Fluid Dynamics For Wide-Size-Fraction Coal Slimes

Flotation is widely used in coal slime cleaning as one of the major ways in mine industry for fine grained minerals.In this paper,a new type wide-size-fraction coal flotation machine was designed by creating different liquid environment for fine grained conventional coal flotation and coarse grain of fluidized flotation in the same machine through the combination of fluidized mechanism and wide-size-fraction coal flotation in view of the problems in coal slime cleaning and drawing lessons from forefathers’ research results.The amplifier design and industrial application from a small laboratory flotation machine to the industrial flotation machine was achieved using similar shape structure and the fluid dynamic characteristics similar principles.The results show that the-1mm coal slimes can be effectively floated with this wide-size-fraction coal flotation machine,which provides a referenced technological approach for coal slimes cleaning.A large number of research work and theoretical exploration was carried out on the structural design and fluid numerical simulation of wide-size-fraction coal flotation machine.The main contents and creative work are as follows.(1)The coarse coal slimes were effectively floated in view of the fluid environment proposed in this paper.The requisite critical rising water flow speed of particles with different density and particle size sticking to different air bubbles keeping suspension in the rising water flow was calculated by the analysis of the particles-air bubble aggregation motor process in the weak rising water flow.The relation model between the critical rising water flow speed,particle size,density and bubble diameter was built.That is(?).The maximum flotation size of slimes in the fluidize flotation process was forecasted.The theoretical basis that the upper particle slimes size can be broadened by introducing fluidization in the slimes flotation process.(2)A new type wide-size-fraction coal flotation machine was designed by creating different liquid environment for fine grained conventional coal flotation and coarse grain of fluidized flotation in the same flotation machine through the combination of fluidized mechanism and wide-size-fraction coal flotation.The laboratory small flotation machine whose diameter is 150mm,height is 300mm;volume is 5L was made.FLUENT 6.3.26 software was employed for the numerical simulation,and the flow field in the flotation machine was analyzed from the velocity and turbulent intensity.The results show that the fluid mechanical conditions for fine and coarse coal flotation can be created in the same machine by dividing the inner fluid field into low speed,weak turbulence and high speed,strong turbulence area after adding the grille board,which can increase the sticking probability between particles and air bubble.In the upper region of the grille board,the low speed,weak turbulence for the coarse slimes fluidization flotation was formed in the rising water flow,which created the different liquid environment for fine grained conventional coal flotation and coarse grain of fluidized flotation in the same flotation machine.(3)The laboratory small wide-size-fraction coal flotation machine testing system was built and the-1mm slimes flotation test of ZhangCun coal preparation plant was carried out.It was shown that the flotation clean coal ash increases with the decrease of the feed size,while the tailing ash with 0.25-0.5mm fraction size is higher than the other two(0.5-1mm,0-0.25mm).The flotation clean coal ash is 10%;the yield is 85%under the conditions that the feed content of flotation machine 0.36m3/h,the rotating speed of the vane 980rpm,the feed pulp density 100g/L.The tailing ash is above 50%.Both the flotation clean coal index number and combustible body recovery is above 90%.And the flotation clean coal ash is under 10%,the yield is 85%under the conditions that the feed content of flotation machine 0.12m3/h,the rotating speed of the vane 980rpm,the feed pulp density 200g/L.The tailing ash is above 55%.Both the flotation clean coal index number and combustible body recovery is also above 90%,which indicates that-1mm under the flotation conditions of large feed content,low concentrate and small feed content,high concentrate can be effectively floated in this wide-size-fraction coal flotation machine.(4)The industry flotation machine whose diameter is 4.25m,height is 4m;volume is 45m3 was designed using similar shape structure and the fluid dynamic characteristics similar principles.And the flow field numerical simulation on the industry flotation machine was carried out.It was shown that the amplifier industry machine has the similar flow field with the small laboratory one,thus creating the fluid mechanical conditions for fine and coarse coal flotation in the same machine,which proved that the design structure of the amplifier flotation machine under the proposed dynamics characteristics parameter has the similar fluid form with the original one and the flotation for fine coal and coarse coal can be effectively realized in the same flotation machine.(5)The first installation and debugging of industry flotation machine and its industry application was accomplished in ZhangCun coal preparation plant.The results show that the flotation clean ash under 8.5%,clean coal yield above 80%,tailings ash content above 50%can be achieved for conventional fraction size slimes flotation.While the flotation clean ash under 10%,clean coal yield above 80%,tailings ash content above 45%can be achieved for wide size fraction slimes flotation.The innovation points of this work are as follows.(1)The flotation process kinematic model between particles and air bubbles aggregation in the weak rising water flow was built and its validity was verified based on its stress analysis.The quantitative relation between the slimes particle size under the condition of fluidization flotation and the upwelling speed was forecasted.The feasibility that the upper limit particle size of the flotation slimes could be increased with fluidization flotation method was proved,which establishs a theoretical foundation for the design of wide-size-fraction coal flotation machine.(2)The fluidized mechanism was applied to wide-size-fraction coal flotation process.The different liquid environment for fine grain coal and coarse grain fluidized flotation achieved and controlled by partition flotation in the same machine was designed and manufactured.The-1mm wide size fraction flotation machine structural design was achieved.On this basis,the similar shape structure and the fluid dynamic characteristics similar amplification methods was proposed.The industrial scale-up design of the wide-size-fraction coal flotation machine was achieved.(3)The industry application system of the wide-size-fraction coal flotation machine was established.The industrial test shows that the-1mm fraction slimes float effectively in this machine.The research results pvovide a referenced technological approach for coal slimes flotation process.